1. Technical Field
The invention relates to the field of night viewer type devices for enhancing the image of a scene to be viewed, and more particularly to weapon mounted night viewer devices suitable for combined use with known man-portable weapon sights.
2. Background Art
Single unit day/night sights have been used by military and law enforcement personnel to aim weapons used in both day time and night time conditions. Typically, a day/night sight includes an objective lens, a reticle and an eyepiece in series with parallel, but separate, day and night channels. A channel selector or optical switch may be used to alteratively direct an image of a target into the day or night channel.
In a day/night sight, the objective lens and the eyepiece may be telescopic to provide a magnified image of the target. The day channel generally uses ambient light to generate an image of the target. The image may be projected or electronically conveyed to a display or to a ocular lens assembly to be viewed by the user. The night channel generally includes an image intensifier to generate an illuminated image of the target. The illuminated image may be likewise projected or electronically conveyed to a display during night time use to be viewed by the user.
Risley prisms have been used in the daylight optical path of the prior dual path devices. U.S. Pat. No. 6,169,628 and U.S. Pat. No. 6,172,821 teach such a day/night scope with Risley prism located in the day branch of the parallel optical path. U.S. Pat. No. 6,111,692 similarly teaches the use in another day/night scope of a Risley prism located in the optical path between the objective lens and a movable focus cell group.
A problem with day/night and other types of combined sights is the bulk and the added weight of two sighing systems that must be carried when the unit is being used in the field.
Also, U.S. Pat. No. 6,111,692 and others disclose in general moving a focus cell lens group in the X-Y-Z dimensions or directions relative to a night path or channel of a day/night scope. Such movement of the focus cell in devices similar to that disclosed in U.S. Pat. No. 6,111,692 was accomplished through the use of an eccentric cam and pin arrangement limiting fore and aft movement of the focus cell to correspond to the rotation of the cam.
While the above cited references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.